High-Dose vs Standard Ergocalciferol for Vitamin D Normalization in Aggressive Non-Hodgkin Lymphoma

Inclusion Criteria: * Age ≥ 20 years. * Newly diagnosed aggressive non-Hodgkin lymphoma, confirmed by histopathological examination according to the WHO Classification of Haematolymphoid Tumours, 5th edition, with an indication for standard first-line chemoimmunotherapy * Eastern Cooperative Oncology Group (ECOG) performance status of 0-3. * Serum 25-hydroxyvitamin D level \< 30 ng/mL within 14 days prior to randomization. * Adequate organ function to receive full-dose standard chemotherapy. * Ability to provide written informed consent. Exclusion Criteria: * Mild hypercalcemia (corrected Ca \> 10.4 mg/dL) * Hyperphosphatemia (PO4 \> 4.5 mg/dL) * History of urolithiasis associated with hypercalciuria or a diagnosis of primary hyperparathyroidism. * Chronic kidney disease stage 4 or higher (estimated glomerular filtration rate \[eGFR\] \< 30 mL/min/1.73 m²). * Inability to take oral medication, active gastrointestinal bleeding, or malabsorption syndrome. * Pregnancy or breastfeeding. * Prior systemic therapy for lymphoma. * Ongoing tumor lysis syndrome requiring urgent treatment. * Prior use of vitamin D supplements (ergocalciferol or cholecalciferol). Withdrawal Criteria: * Development of mild hypercalcemia. * Development of mild hypophosphatemia. * Development of hypervitaminosis D. * Occurrence of severe adverse events (AEs) or side effects for which the investigator considers discontinuation of the study drug necessary for patient safety. * Investigator's judgment that continued participation may pose a safety risk, such as the occurrence of serious infection, febrile neutropenia, or organ failure. * Non-adherence to study medication, defined as cumulative vitamin D₂ intake of less than 80% of the expected cumulative dose at the time of serum vitamin D assessment. * Participant withdrawal of consent to continue participation in the study.